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Besieging A Pipolsid Bunker City 
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Post Besieging A Pipolsid Bunker City
Ok, so the idea is that a Pipolsid city is under attack by both Loroi and Umaik.

The aggressors control the orbitals and their purpose is to obtain a mcguffin (Let's say, the power of friendship) from said city. And, they'd want it in tact, for obvious reasons.

The Pipolsid are habitating a deep underwater city and, uh, are just gonna fight them on this one despite it being out of charachter.

The Major Pipolsid cities have, in anticipation of the attack, which they saw coming far in advance, moved their cities and major industries five miles under their planet's oceans. They use deep underwater vents to grow genetically modified algae to sustain them, and they also supplement their food source with shallow water aquaculture.

For this scenario, we'll assume they have far superior water craft and sea power than their enemies. Also, we'll ignore any existing Loroi infrastructure in Pipolsid space, and say the enemies have to bring in resources from outside the system or build said resources on sight.

The question here is, what would it take for the Loroi/ Umaik to take the city?

The premise here is that nukes aren't going to be effective, (justification below), unless they can float down to incredibly close range to said underwater cities, and, as mentioned before, the Pipolsid already have the advantage in the water, and Pipolsid ability to act deep underwater essentially blinds the enemy to their movements.

Starting out, the pipolsid have no active space ships, but they retain the knowledge and industries to build them and associated tech, but they can build them only on the planet, they won't magically be teleported into an orbital.

So, short of dropping a KT asteroid on the place, how would you, if commanding the attacking force, try to take the city?

On the other hand, how would you, if you were the Pipolsid force, defend against these tactics? What would, or even could, you do if the enemy did just decide to drop an asteroid or several million tons of antimatter on your planet?

What logistical difficulties, if any, would the attacking forces face in trying to contain and transport several million tons of antimatter?

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Last edited by White on Tue May 28, 2019 11:34 pm, edited 5 times in total.



Tue May 28, 2019 11:09 pm
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Post Re: Besieging A Pipolsid Bunker City
Here's what I, and Arioch, have said on the subject so far.

White wrote:
If so, it makes me wonder how difficult a seige of a Pipolsid city would be.

My sense is that anything several miles under an ocean is essentially nuke proof if they can maintain even local defences. And I doubt any race in the bubble has better underwater craft than the pipolsid. On the other hand, I'm not sure how powerful and effective anti matter would be. I remember reading that Turning on the engines of a warship inside an atmosphere would devestate the ecology, but I'm not sure what that means.

Would it mean that the ship could just fly by in the upper atmosphere and an extinction level event happens, or would it have to swim down to within several miles of a deep underwater Pipolsid city, exposing itself to enemy fire all the while?


Arioch wrote:
The Pipolsid structures (especially with high technology) allow them to live at almost any depth. Their flexible bodies can withstand variable pressures without much problem. However, they rarely live in the very deep ocean, as there's not much there to eat.

Being underwater will definitely give you some resistance to airbursts or attacks against ground targets, but whoever attacked Lenzano knew who their targets were, and adjusted their methods accordingly. I don't know that much about hydrodynamics, but I can infer from how depth charges work that the shock waves from sub-surface detonations can be very damaging. Still, it can be hard to find targets in deep water, and Lenzano has better than average survival of relics from that era.



White wrote:
I'm not an expert on hydrodynamics either, but from what I've read on the topic, which, admittedly, isn't much, there seems to be a qualitative difference between deep underwater explosions and those happening in relatively shallow water.

If I had to guess, and this is my own theorizing at this point, since a shock wave, I think, is essentially a really large amplitude of a sound wave, one which leaves behind a vacuum because the atmospheric density isn't high enough to maintain a sound wave against such a pressure, than explosions underwater should be devastating, but limited in effect. You wouldn't get a miles wide blast zone like you get in the atmosphere, just a compact explosive area beyond which you'd just be left with really loud sound waves.

If anyone knows about this topic, just let me know if I'm wrong.

Actually, I think I'll just create a new topic for this idea.

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Tue May 28, 2019 11:14 pm
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Post Re: Besieging A Pipolsid Bunker City
I don't think TL10+ naval torpedoes would have any difficulty delivering high yield warheads regardless of the depth, but since you have specified in your scenario that the mcguffin must be taken intact, antimatter bombs and orbital strikes are off the table anyway. So the only option is to bring marines down in deep submersibles and attempt to breach and board the bunker. However, since you've also specified that the defenders have superior watercraft, that will probably be impossible.

I don't see any other options.

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Thu May 30, 2019 1:24 am
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Post Re: Besieging A Pipolsid Bunker City
At 5 miles (8km) under water, assuming an Earth-equivalent planet, the pressure is going to be ~800bar (that's over 11600 psi). I think that alone makes any meaningful fighting or bunker breaching operations impossible, even if the attackers can bring down marines in submersibles in sufficient numbers.

If it were in more shallow waters, say, a few hundred meters deep, the two attackers would probably use their preferred tactics: The Loroi would send in a couple of small Teidar commando teams to telekinetically kill any opponents and breach the compound, while the Umiak would just use Moar Dakka and overwhelm any Pipolsid defenses.


Thu May 30, 2019 2:33 am
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Post Re: Besieging A Pipolsid Bunker City
Are you in a rush?


Plan Fast - drop a KT+ impactor on the opposite side to force mass vulcanism in the target zone, swallowing the city

drop a KT+ impactor above the city, maybe directly impacting it, and forcing mass vulcanism...

drop multiple sub-KT masses in coordinated waves to generate devastating shockwaves at every sharp transition zone; shortly before impact, release hunter-killer torpedoes on timers to kill anything that moves in the target zone: design them to die when they get too deep, but have each wave designed for a deeper area; follow the last wave with your marines.

Note: if excessively ambitious, and very lucky, then you may be able to pump vast amounts of water out of the relevant body of water by preemptively building moronically durable levees at strategically chosen points: do something smart instead.

Also note: don't worry over prisoners, 50/50 chance you killed them all. Oh, and I hope you weren't planning to go fishing.


Plan Slow - build huge flotillas of mirrors, and just keep patrolling for a while. When the seas finish boiling away, raid the target.

Note: I hope you weren't planning to go fishing.


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I suppose you could always build a KT-mass worth of super-cavitating KK torpedoes, load them into a huge cargo crate with too many torpedo launchers, and carefully lower it into the water before letting it just sink. Then just follow it with your primary combat forces, as it kills everything that doesn't move. If the torpedoes are stupidly simple, then it might even be practical for space-faring civilizations.

Note: depending what you ran those torpedoes off of, you might want to restrict fishing to the other side of the planet.


Thu May 30, 2019 7:42 pm
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Post Re: Besieging A Pipolsid Bunker City
Arioch wrote:
I don't think TL10+ naval torpedoes would have any difficulty delivering high yield warheads regardless of the depth
Absalom wrote:
I suppose you could always build a KT-mass worth of super-cavitating KK torpedoe


How quickly would those torpedoes be able to swim through the atmosphere and water that they'd avoid being shot down?

Or am I underestimating the effective range of their explosions?

Absalom wrote:
Note: if excessively ambitious, and very lucky, then you may be able to pump vast amounts of water out of the relevant body of water by preemptively building moronically durable levees at strategically chosen points: do something smart instead.


I feel that if you were ambitious and lucky enough to construct a mega structure in the very waters you were trying to invade, you could probably just mount a straight invasion, to be honest.

As for my tactic, I'd think the Umaik would just colonize the land portions of the planet, and then turn that part of it into a large industrial base where they'd just make a mountain load of cheap ships to zerg rush the city. I imagine that the oceans would have, as much, if not more resources, but if the Umaik ships stick to shallow waters initially, than they could, I would think, drop bombs from that higher altitude, forcing Pipolsid craft up to fight them at said higher altitude, where they would be able to call support from air bound ships.

The Loroi would be key in actually locating the cities/ bases of operation.

Just tell me if you see anything wrong with that plan.

Absalom wrote:
drop multiple sub-KT masses in coordinated waves to generate devastating shockwaves at every sharp transition zone; shortly before impact, release hunter-killer torpedoes on timers to kill anything that moves in the target zone: design them to die when they get too deep, but have each wave designed for a deeper area; follow the last wave with your marines.


That's a fun idea!

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Fri May 31, 2019 2:21 pm
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Post Re: Besieging A Pipolsid Bunker City
White wrote:
How quickly would those torpedoes be able to swim through the atmosphere and water that they'd avoid being shot down?

Or am I underestimating the effective range of their explosions?

Shooting down the torpedoes in atmosphere is not an option, since the defenders have retreated underwater.

"Shooting down" torpedoes underwater is a difficult proposition; the same properties of water that prevent the invaders from using direct-fire weapons also prevent the defenders from using them. You'd need some kind of anti-torpedo torpedo. Assuming for a moment that such a thing could be practical, such defenses could either be overwhelmed through numbers, or avoided through the use of countermeasures and quiet torpedoes. Since the bunkers aren't moving, the offensive torpedoes don't have to be fast, so they can be very quiet.

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Fri May 31, 2019 3:12 pm
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Post Re: Besieging A Pipolsid Bunker City
Arioch wrote:
White wrote:
How quickly would those torpedoes be able to swim through the atmosphere and water that they'd avoid being shot down?

Or am I underestimating the effective range of their explosions?

Shooting down the torpedoes in atmosphere is not an option, since the defenders have retreated underwater.

"Shooting down" torpedoes underwater is a difficult proposition; the same properties of water that prevent the invaders from using direct-fire weapons also prevent the defenders from using them. You'd need some kind of anti-torpedo torpedo. Assuming for a moment that such a thing could be practical, such defenses could either be overwhelmed through numbers, or avoided through the use of countermeasures and quiet torpedoes. Since the bunkers aren't moving, the offensive torpedoes don't have to be fast, so they can be very quiet.


Or they could be big rocks.


Fri May 31, 2019 4:25 pm
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